[DeckApe]

Tube socket obtained; discovered the magic behind the retaining ring that allows for the socket portion to be rotated to the correct keyhole orientation. Next challenge:

Is there any reason I can't take a couple of screws and nuts to attach the new socket instead of attempting to replace the metal grommets? The only down side to this method is that I will have to drill a hole in the chassis for the grid cap wire. (I'll probably drill it big enough that I can slip a rubber insulating grommet into the hole, ensuring isolation of the 'cap wire.)